Pump, In Particular Pneumatic Pump

ABSTRACT

The invention relates to a pump comprising a housing ( 2 ), comprising at least one pump chamber ( 15 ), comprising in inlet valve ( 30 ) that has a valve element ( 30   a ) which controls an inlet opening ( 30   c ), comprising an outlet valve ( 33 ) that has a valve element ( 33   a ) which controls an outlet opening ( 33   c ), comprising a pressure relief valve ( 43 ) that has a valve element ( 43   a ) which controls a pressure relief opening ( 43   c ) and on which a spring element ( 48 ) acts in the closing direction ( 31 ), and comprising a spring chamber ( 49 ), that receives the spring element ( 48 ) end that faces away from the closing direction resting against the stop element.

The invention refers to a pump, in particular to a pneumatic pump.Pneumatic pumps are used in the automotive sector, for example, forfilling the seat bladders with air to change the contour of the seat'ssitting and backrest areas. A pump used for the purpose named above, forexample, has at least one pump chamber. By enlarging and reducing thechamber volume with the help of a drive unit, surrounding air issuctioned into the pump chamber during volume enlargement and air isdriven out from the pump chamber during volume reduction. To control thecorresponding air flows, the pump is equipped with an inlet valve thathas a valve element for controlling the inlet opening. The inlet valveopens autonomously when the pump chamber enlarges and air flows into itfrom the surroundings. An outlet valve serves for controlling theoutgoing airflow. It is likewise equipped with a valve element, but itcontrols an outlet opening which opens when air is driven out of thepump chamber.

A pump of the type described above is additionally equipped with apressure relief valve used especially when a vehicle's seat bladders arebeing filled because they can leak under an excess pressure load. Thepressure relief valve, in turn, has a valve element that closes apressure relief opening and in closing direction rests on a springelement arranged in a spring space. When the pressure in the pumpchamber exceeds a preset limit value, the excess pressure valve openswhen there is a limit pressure set by the spring element. With regard tothe respectively permissible maximum pressure of the pneumatic system orof a designed part thereof, the limit pressure can vary depending on theapplication. So far, the approach has been to use springs of variousstrengths in the assembly of the pump, but this entails a correspondinglogistical and technical assembly effort. Additionally, there is therisk of that the wrong springs could be fit into the pump duringassembly.

The task of the invention is to suggest a pump of the type describedabove to remedy this situation.

This task is solved according to claim 1 by arranging a stop elementaccessible from the external side of the housing and movable in closingdirection on which the spring element can rest with its end pointingtowards the closing direction. In this way, the required limit pressurecan be easily adjusted during assembly by building in a spring elementin the spring space that can be universally used for limiting thepressure range. Afterwards, the stop element is brought into the springspace and while a pressure corresponding to the limit pressure isapplied on the pump—is positioned with regard to its distance to thevalve element in such a way that the desired limit pressure is reached.When doing so, deviations from limit pressure resulting frommanufacturing tolerances can be compensated.

In an especially preferred design variant (particularly advantageous inpump housings made of plastic) it is foreseen for the inner wall of thespring space to have a regulating area extending along the closingdirection by holding the excessively dimensioned stop element in aclamped way with regard to the regulating area, whereby the spring spacehas an actuating opening through which the stop element advancing inclosing direction is accessible with a tappet or the like, for example.In this case, the clamping force can be chosen through correspondingdimensional ratios in such a way that the stop element impinged on bythe spring element against the closing direction is reliably held in theintended position in the adjustment area. Depending on the chosen excessof the stop element, a more or less elastic and/or plastic deformationof the stop element takes place and/or of a housing wall thatcircumscribes the spring space. Particularly in the case of housingsmade of soft materials such as plastic, a stop element made of amaterial harder than the one used for the pump's housing or for thehousing wall that circumscribes the spring space is advantageous. Here,the stop element is pressed into the material of a housing wall thatcircumscribes the spring space. A metallic stop element is preferablyused.

Seen in top view in closing direction, the stop element has acomplementary shape to the inner transversal shape of the adjustmentarea. One result of this is the accomplishment of a sealing of thespring space towards the surroundings and another result is a higherclamping effect. Penetration of humidity into the spring space, forexample, is thereby prevented.

Preferably, a stop element executed as a sphere is used, in which casethe adjustment area that acts together with the stop element iscircularly cylindrical, i.e. forms the surface shell of a circularcylinder. This design rules out a wrong assembly caused by erroneouslypositioning the stop element in the spring space, for example in a wrongturning position with regard to an axis running parallel to the closingdirection.

When pressure relief valves of the type used here open, this isaccompanied most of the time by the generation of noise. In at least onedesign variant independent from the spring space and stop elementdesigns, noise reduction is achieved by having the lower-pressure sideof the pressure relief valve end in the spring space. With regard to itssurroundings, the spring space can be fully closed so there is no fluidconnection to the atmosphere and therefore the propagation of anairborne noise generated inside the spring space is prevented fromreaching the exterior. Even if the spring space is connected to thesurroundings through a bore hole to allow pressure to equalize betweenspring space and surroundings—as is the case in a design variant—ifexcess pressure occurs, this bore hole can have a very small flowcross-section. It is different with the inlet opening, whose flowcross-section cannot be reduced at will so that an airborne noisegenerated in the pressure relief valve can propagate almost unhinderedinto the surroundings.

The pressure-equalizing bore hole that connects the spring space to thesurroundings mentioned above can be done completely without if thespring space is connected to the inlet opening, in which case its endlocated upstream (i.e. its entrance opening) does not end directly inthe surroundings but in a housing space of the pump in which one driveunit for actuating the pump is arranged. In doing so, the drive unitacts like the insulating material in a sound absorber to eliminate thenoise. However, in conventional pumps of the type presented here, theinlet opening is separated by a duct wall of the other housing spaces.

The invention will now be explained in more detail with the help of theenclosed drawings, which show:

FIG. 1: A perspective lateral view of a pump with a housing encompassingone upper part of the housing, one lower part of the housing, an upperand a lower support, and a motor,

FIG. 2: An exploded view of the pump shown in FIG. 1,

FIG. 3: A perspective view of the housing's upper part,

FIG. 4: A perspective view of a valve membrane arranged between theupper part of the housing and the upper support,

FIG. 5: A perspective view of the upper support,

FIG. 6: A longitudinal cut through the pump housing with a cutting linecorresponding to line VI-VI in FIGS. 4 & 5,

FIG. 7: A longitudinal cut through the pump housing with a cutting linecorresponding to line VII-VII in FIGS. 4 & 5,

FIG. 8: A longitudinal cut through the pump housing with a cutting linecorresponding to line VIII-VIII in FIGS. 4 & 5,

FIG. 9: A partial sectional view of another embodiment of a pump, inwhich the spring space is connected to the surroundings via a bore hole;

FIG. 10: A sectional view of the pump of FIG. 9, but shown from anotherangle.

To explain the invention, exemplary reference is made to a pneumaticpump, in which case the designs described also apply to pumps forfluids. The pump 1 shown in the illustrations is intended to beinstalled in a vehicle seat and serves for filling seat bladders tochange the contour of a vehicle seat in the sitting or backrest area,for example. The pump 1 comprises a housing 2 (especially made ofplastic) on which an outlet connection piece 3 has been form-fitted. Theside of the housing 2 supporting the outlet connection piece 3 will alsobe referred to as upper side 4 below. A motor 6, especially an electricmotor, has been flanged onto the lower side 5 of the housing 2. Thehousing 2 comprises an upper part 7 and a lower part 8, in which casethe upper part 7 supports the connection piece 3 and forms the upperside 4. Two plate-shaped supports—namely an upper support 9 and a lowersupport 10—are clamped sandwich-like between the upper part 7 and thelower part 8. Between the upper support 9 and the upper part of thehousing 7, a plate-shaped valve membrane 13 made of an elastic material(e.g. a rubbery polymer) has been clamped in. Four pot-shapeddepressions that create pump chambers 15 have been form-fitted in thepump membrane. In its upper border, the pump membrane 14 has acircumferential bulge 16 clamped between the upper support 9 and thelower support 10. On the upper part of the housing, peripheral arms 18extending downwards have been form-fitted along the middle longitudinalaxis 17 of the pump. On the free end of two diametrically opposing arms18, a rear grip element 18 has been fixed or form-fitted that, bycreating an axially effective positive-locking fit, grips an opposingelement 20 on the lower part of the housing 8 from behind. As a resultof this, the valve membrane 13, the upper support 9, the pump membrane14 and the lower support 10 are axially tensed between the upper part ofthe housing 7 and the lower part of the housing 8. In the lower part ofthe housing 9, there is a turnstile 23 obliquely positioned with respectto the middle longitudinal axis 17 that has been mounted on an eccentric25 with an axis 24 protruding from its underside. The eccentric 25, inturn, is connected in a fixed rotary way to a drive shaft 26 of themotor 6. The pump membrane 14 has on the underside, in the area of thepump chambers 15, a tappet-shaped extension 27 with a head-shaped end 28fixed in a recess 29 of the turnstile.

Each pump chamber 15 is assigned to an inlet valve 30 and an outletvalve 33. The outlet valves 33 are arranged in an outlet port 34 thatextends inwards from the pump chamber 15 all the way to the inletconnection piece 3 and finally ends in the surroundings. The inletvalves 30 are arranged in an inlet port 35 in which—with respect to theinflow direction 36—suctioned air flows towards the pump chamber, theend 37 located upstream ends in a housing space 38, in which a driveunit 39 for actuating the pump chambers 15 (i.e. for enlarging andreducing them), in this case the turnstile 23 and the eccentric 25, arearranged. The inlet valves 30 and the outlet valves 33 have in each casea valve element 30 a that is freely cut as tongue-shaped parts from avalve membrane 13 forming an entire membrane and that in each casecontrols an inlet opening 30 and an outlet opening 33 c located in theupper support 9. Each one of the valve elements 30 a acts with a sealseat 30 b protruding from the underside of the upper part of the housing7 (FIGS. 3 & 6). The seal seats 30 b are sections of a ring-shapedclosed seal seat 32 that separates the lower pressure side of the pump 1from its pressurized side. The valve seats 33 b assigned to the outletvalves 33 protrude from the upper side of the upper support 9. In thesituation shown in FIG. 7, the valve element 33 a lies on top of thevalve seat 33 b that encompasses the outlet opening 33 c.

On the upper side of the valve membrane 13, all inlet ports 35 end in acollecting space 41 (located above the valve membrane 13) arrangedcentrally on the pump in the direction of the arrow 40 in FIG. 1 in thetop view. The collecting space 45 is circumscribed towards the top bythe upper part of the housing 7 and towards the bottom by a central areaof the valve membrane 13 that comprises the valve elements 30 a of theinlet valves 30.

Apart from the inlet and outlet vales 30, 33, the pump 1 is equippedwith a pressure relief valve 43 developed between a central area of thevalve membrane 13 that forms a valve element 43 a and a seal seat 43 bof the upper support 9. The valve element 43 b is centrally arranged inthe collecting space 41 and interfused by a central connection opening44. Thus, the valve element 43 a is the peripheral area of the valvemembrane 13 that circumscribes the connection opening. The valve element43 a lies on a ring-shaped seal seat 43 b of the upper support 9 thatcircumscribes the pressure relief opening 43 c. To increase the sealingeffect, the peripheral area mentioned above has a sealing lip 45 on itsunderside. An opening 42 a interfused with the pump membrane 14 islocated centrally in the latter. Below the opening 45, the central areaof the pump membrane 14 surrounded by the pump chambers 15 is supportedby an area 42 of the lower support 8 that bulges out upwards, in whichcase it is also interfused with an opening 46. Thus, the section of theinlet port 35 extending away from the valve element 30 a of the inletvalves 30 against the inflow direction 36 is created by the collectingspace, the connection opening 44 and subsequent openings 44, 43 c, 42 aand 46, in which case the inlet port 35 ends with the opening 46 in thehousing space 38, which is circumscribed by the lower support 10 and thelower part of the housing 8.

A largely cylindrical connection piece 47 open towards the upper side ofthe housing 4 juts out from a central position of the upper part of thehousing 7. The interior of the connection piece creates a spring space49 for receiving a spring element 48, namely a threaded compressionspring. On its front side facing away from the upper part of the housing7, the connection piece 47 has an assembly opening 50 over which thespring element 48 can be inserted into the spring space 49. The springelement 49 supports itself with its lower end on the valve element 43 aof the pressure relief valve 43 by means of an intermediate layer of asupporting ring 52, thus impinging on the former in closing direction31. The other end of the spring element 48, on the other hand, supportsitself on a stop element 51 arranged on a fixed axis (with respect tothe medium longitudinal axis 17, inside an adjustment area 53 formed bya longitudinal section of the inner wall 54 of the spring space 49). Theaxially fixed fixation of the stop element 51 is accomplished by makingits dimension transversal to the medium longitudinal axis 17 slightlylarger than the inside diameter of the adjustment area 53. In theexamples shown in the drawings, the inner wall 54 of the adjustment areais cylindrical or extends on the outer surface of a cylinder and has aninside width or diameter 55 that is smaller than the dimension of thestop element 51 in a direction running transversally to the mediumlongitudinal axis 17. The stop element 51 is preferably a metallicsphere with a diameter 56 slightly larger than the inner diameter 55 ofthe adjustment area 53. Owing to the dimensions mentioned above and theconnection piece's softer plastic material compared to the metallicsphere, the stop element 51 digs itself into the contact area 57 byforming a ring-shaped cavity 58 in the inner wall 54 of the connectionpiece 47. The dimension relationships mentioned above have been chosenin this case so that the clamping force with which the stop element 51is held in the adjustment area 53 is larger than the force exerted bythe spring element 48 in axial direction. To set a certain limitpressure (i.e. a pump chamber pressure) to which the pressure reliefvalve 43 should react, the stop element 51 is inserted into the springspace 49 through the assembly opening 50 while the pump is beingassembled and moved in closing direction 31 until the spring forceexerted by the threaded compression spring 48 correlates with thedesired limit pressure.

In the design variant shown in FIGS. 9 & 10, the spring space 49′ is notconnected to an inlet port. Here, the pressure between the spring spaceand the surroundings is compensated through a connection opening 59interfused with the wall of the connection piece 47. As in the designvariant described above, the valve element 43 a lies on a ring-shapedseal seat 43 b′, though it does not border an opening but merely arecess 60 closed towards the bottom. The inlet port (not shown) istherefore not connected to the spring space 49.

The way the pump works will now be explained: When the air from thesurroundings or from the housing space 38 is suctioned, it enlarges thepump chambers 15 by moving the extensions 27 of the pump membrane 14downwards. The air [flows] through the openings 46, 42 a, 43 c and 44into the collecting space 41 (arrows 63) and from there through theinlet valves 30 to the pump chambers 15 (FIG. 6). When this occurs, thevalve element 30 a is elastically deformed and moved downwards (arrow64) and as this happens, it lifts off the seal seat 30 b. The valveelements 30 a and the valve elements 33 a of the outlet valves 33 arenot as thick as the remaining valve membrane 13, so that in each case afree space is created above and below the valve elements that allows thevalve elements to be lifted from the respective valve seat.

If the extensions 27 move upwards, the pump chambers 15 are made smallerand air is driven out of them. The air that was driven out flows throughthe outlet openings 33 c in accordance with arrow 66 in FIG. 7 andreaches a pressure space (see also FIG. 3) bordered by the valvemembrane 13, the upper part of the housing 7 and the seal seat 32. Thepressure space is connected to the outlet port 34 of the outletconnection piece 3.

If excess pressure exceeds the limit pressure, the pressure relief valve43 reacts. When this occurs, the valve element 43 a is lifted off thevalve seat 43 b, 43 b′, so air can reach the spring space through theconnection opening 44 available in the valve element 43 a. In the designvariant shown in FIGS. 9 and 10, pressure is compensated with thesurroundings through the connection opening 59, otherwise via the inletport 35. The impingement of the valve element 43 a with excess pressuretakes place through another pressure space 68 arranged below the valvemembrane and bordered by it and the upper support 9. The pressure space67 mentioned above arranged above the valve membrane is connected to thepressure space 68 arranged below the valve membrane through openings 69.

1. Pump with a housing (2), with at least one pump chamber (15), with aninlet valve (30) equipped with a valve element (30 a) that controls aninlet opening (30 c), with an outlet valve (33) equipped with a valveelement (33 a) that controls an outlet opening (33 c), and with apressure relief valve (43) equipped with a valve element (43 a) impingedon a spring element (48) in closing direction (31) that controls apressure relief opening (43 c), and with a spring space (49) thatcontains the spring element, whereby a stop element (51) movable inclosing direction (31) and accessible from the outer side of the housingis arranged, on which the spring element (48) supports itself with itsend pointing against the closing direction, the inner wall (54) of thespring space (49) having an adjustment area (53) that extends along theclosing direction (31) in which the excessively dimensioned stop element(51) with regard to the adjustment area (53) is held in place byclamping, in which case the spring space (49) has an assembly opening(150) through which the stop element is accessible for advancing towardsclosing direction, the stop element (51) being a sphere and that theinner wall (54) of the adjustment area (53) extends on a circularcylinder surface. 2-3. (canceled)
 4. Pump according to claim 1,characterized in that the stop element (51) is made of a material thatis harder than the material of a housing area that circumscribes thespring space (49).
 5. Pump according to claim 4, characterized in thatthe housing (2) of the pump is made of plastic.
 6. Pump according toclaim 4, characterized in that the stop element (51) is made of metal.7. (canceled)
 8. Pump according to claim 1, characterized in that thelower-pressure side of the pressure relief valve (43) ends in the springspace (49).
 9. Pump according to claim 8, characterized in that thespring space (49) ends in the surroundings through a connection opening(59) in a wall circumscribing it.
 10. Pump according to claim 8,characterized in that the spring space (49) is connected to the inletport (30).
 11. Pump according to claim 10, characterized in that theinlet port (30) ends in the spring space (49) through a connectionopening (44) in the valve element (43 a) of the pressure relief valve(43).
 12. Pump according to claim 11, characterized in that a borderarea circumscribing the connection opening (44) of the valve element (43a) is pressed by the spring element (48) against a ring-shaped seal seat(43 b) that encompasses a pressure relief opening (43 c).
 13. Pumpaccording to claim 8, characterized in that the end of the inlet port(30) located upstream ends in a housing space (38) of the pump (1), inwhich a drive unit (39) that serves to drive the pump is arranged. 14.Pump according to claim 8, characterized in that the valve elements (30a, 33 a, 43 a) are part of a one-piece valve membrane (13) clampedbetween an upper part of the housing (7) and a support (9) supportingthem.
 15. Pump according to claim 8, characterized in that it hasseveral pump chambers (15), in which case they are distributed aroundthe centrally arranged pressure relief valve (43) when seen in top viewin closing direction (31).
 16. Pump according to claim 8, characterizedin that the at least one pump chamber (15) is made up of a flexible pumpmembrane (14).